Chapter 2

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1

dietary importance of carbohydrates

widely available, low cost, easily stored

2

energy production system

-digests carbohydrates to produce glucose

-absorbs glucose and transports it to cells

-energy is released from cellular metabolism

3

saccharide

carbohydrate class

4

simple carbohydrates

(have 1 to 2 units of sugar) ex. monosaccharides, discaccharides

5

complex carbohydrates

have many sugar units ex. polysaccharides

-the complex forms of dietary carbohydrates are starch and dietary fiber

6

Monosaccharides

-glucose: basic sugar in human metabolism (source corn syrup)

-Fructose: primarily found in fruits and honey

-Galactose: Lactose (milk, milk products)

7

Disaccharides

-Sucrose: table sugar (glucose+ Fructose)

-Lactose: Milk, milk products (Glucose+ Galactose)

-Maltose: product of intermediate breakdown of starch in the body (Glucose+ Glucose)

8

polysaccharides

complex

-starch: Grains and grain products (cereal, bread, crackers, backed goods)

-Glycogen: storage form of carbohydrate in animal tissue (not a dietary source)

-dietary fiber

9

glycogen

a complex carbohydrate found in animal tissue that is composed of many glucose units linked together

-crucial to the body's metabolism and energy balance; found in the liver and muscles where it is constantly recycled

-stores of glycogen help to maintain blood glucose levels

10

dietary fiber

cannot be broken down for energy in humans (important dietary asset)

-diets high in fiber can prevent and treat disease, lower blood cholesterol levels, prevent constipation, increase satiety, slow glucose absorption, protect against disorders of small and large intestine

11

Insoluble Fiber

-prevention and constipation

cellulose: (plant cell walls; holds water) ex. stalk of leaves of vegetables, coverings of seeds

hemicellulose: absorb water and swell to a larger bulk; slowing stomach emptying, binds with bile acids preventing spastic colon ex. bran, whole grains

lignin: (forms woody parts of some plants) ex. broccoli stems, fruits with edible seeds i.e strawberries and flaxseeds

12

starch

most important carbohydrate in the body

ex. rice, wheat, oatmeal, potatoes, corn, beans

13

Dietary fiber recommendations

men age 50 and younger: 38g/day

30g/day for men >50

for women: 25g/day

21g/day for women >50

14

whole grain

food products that are produced form unrefined grain. Unrefined grains retain the outer bran layers, & nutrients (i.e dietary fiber, vitamins, and minerals).

15

Enriched Grains

refined grain products to which some but not all vitamins and minerals that were removed during the refining process- ex. riboflavin, niacin, thiamin, folate, iron-- have been added back to some extent.

16

Fortified Foods

those that have nutrients that would not naturally occur in food regardless of how it was processed (ex. calcium fortified orange juice, many ready to eat breakfast cereals)

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Nonnutritive sweeteners

alternative sweeteners are sugar substitutes that do not have a notable caloric value

ex. acesulfame-K, aspartame, luohan guo, neotame, saccharin, stevia, and sucralose

18

Nutritive Sweeteners

sweeteners that contribute to total calorie intake

-provide 2 to 3 kcal/g

-ex. sorbitol, mannitol, and xylitol

-sugar alcohols are absorbed more slowly and do not raise blood sugar level as rapidly as glucose

19

Digestion of Carbohydrates: Mouth

FIgure 2-4 pg.24

  • muscle actions mechanically break the food mass into smaller particles
  • Chemical Process in which enzymes begin breaking food down (salivary amylase acts on starch to begin its breakdown into dextrins and monosaccharides.
20

Digestion of Carbohydrates: Stomach

  • peristalsis continues the mechanical digestive process
  • gastric secretions do not breakdown carbohydrates but stop action of salivary amylase
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Digestion of Carbohydrates: Small Intestine

  • Peristalsis continues the mechanical breakdown of food in the small intestine
  • Chemical digestion of carbohydrate is completed in the small intestine by specific enzymes from pancreas and the intestine
22

Pancreatic Secretions

  • enter duodenum through the common bile duct
  • secretions contain starch- splitting enzyme pancreatic amylase for the breakdown of starch into disaccharides and monosaccharides
23

Intestinal Secretions

Enzymes from the brush border of the intestinal tract contain three disaccharides: sucrase, lactase, and maltase. These specific enzymes act on their respective disaccharides to render the monosaccharides- glucose, galactose, and fructose- ready for absorption directly into the portal blood circulation to the liver.